Add playground test case.

This test will help with transforming the
current cert_cb into one that handles serialized
reconnects too.

src/lib/Makefile.am

@@ -156,6 +156,7 @@ endif
 check_PROGRAMS = \
   test_exchange_api_keys_cherry_picking_new \
   test_exchange_api_overlapping_keys_bug \
+  test_exchange_api_interpreter_on-off \
   test_exchange_api_new \
   test_auditor_api
 
@@ -200,6 +201,19 @@ test_exchange_api_new_LDADD = \
   -lgnunetutil \
   -ljansson
 
+test_exchange_api_interpreter_on_off_SOURCES = \
+  test_exchange_api_interpreter_on-off.c
+test_exchange_api_interpreter_on_off_LDADD = \
+  libtalertesting.la \
+  libtalerexchange.la \
+  $(LIBGCRYPT_LIBS) \
+  $(top_builddir)/src/json/libtalerjson.la \
+  $(top_builddir)/src/util/libtalerutil.la \
+  $(top_builddir)/src/bank-lib/libtalerbank.la \
+  -lgnunetcurl \
+  -lgnunetutil \
+  -ljansson
+
 test_exchange_api_overlapping_keys_bug_SOURCES = \
   test_exchange_api_overlapping_keys_bug.c
 test_exchange_api_overlapping_keys_bug_LDADD = \

src/lib/test_exchange_api_interpreter_on-off.c

@@ -0,0 +1,127 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2018 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3, or (at your
+  option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public
+  License along with TALER; see the file COPYING.  If not, see
+  <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file exchange-lib/test_exchange_api_keys_cherry_picking_new.c
+ * @brief testcase to test exchange's /keys cherry picking ability
+ * @author Marcello Stanisci
+ * @author Christian Grothoff
+ */
+
+#include "platform.h"
+#include "taler_util.h"
+#include "taler_signatures.h"
+#include "taler_exchange_service.h"
+#include "taler_json_lib.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <microhttpd.h>
+#include "taler_bank_service.h"
+#include "taler_fakebank_lib.h"
+#include "taler_testing_lib.h"
+
+/**
+ * XXX:
+ *
+ * This test helps in finding a way to use/modify the "normal"
+ * cert_cb to handle reconnections from serialized states as well.
+ * 
+ * 1st step: simply turn the interpreter off and on again.
+ * 2nd step: turn the interpreter off and give a serial state
+ *           to reconnect.
+ */
+
+/**
+ * Configuration file we use.  One (big) configuration is used
+ * for the various components for this test.
+ */
+#define CONFIG_FILE "test_exchange_api_keys_cherry_picking.conf"
+
+/**
+ * Exchange base URL; mainly purpose is to make the compiler happy.
+ */
+static char *exchange_url;
+
+/**
+ * Auditor base URL; mainly purpose is to make the compiler happy.
+ */
+static char *auditor_url;
+
+
+/**
+ * Main function that will tell the interpreter what commands to
+ * run.
+ *
+ * @param cls closure
+ */
+static void
+run (void *cls,
+     struct TALER_TESTING_Interpreter *is)
+{
+
+  struct TALER_TESTING_Command commands[] = {
+
+    TALER_TESTING_cmd_end ()
+  };
+
+  TALER_TESTING_run (is,
+		     commands);
+}
+
+
+int
+main (int argc,
+      char * const *argv)
+{
+  /* These environment variables get in the way... */
+  unsetenv ("XDG_DATA_HOME");
+  unsetenv ("XDG_CONFIG_HOME");
+  GNUNET_log_setup ("test-exchange-api-cherry-picking-new",
+                    "DEBUG", NULL);
+  TALER_TESTING_cleanup_files (CONFIG_FILE);
+  /* @helpers.  Run keyup, create tables, ... Note: it
+   * fetches the port number from config in order to see
+   * if it's available. */
+  switch (TALER_TESTING_prepare_exchange (CONFIG_FILE,
+                                          &auditor_url,
+					  &exchange_url))
+  {
+  case GNUNET_SYSERR:
+    GNUNET_break (0);
+    return 1;
+  case GNUNET_NO:
+    return 77;
+  case GNUNET_OK:
+    if (GNUNET_OK !=
+        /* Set up event loop and reschedule context, plus
+         * start/stop the exchange.  It calls TALER_TESTING_setup
+         * which creates the 'is' object.
+         */
+        TALER_TESTING_setup_with_exchange (&run,
+                                           NULL,
+                                           CONFIG_FILE))
+      return 1;
+    break;
+  default:
+    GNUNET_break (0);
+    return 1;
+  }
+  return 0;
+}
+
+/* end of test_exchange_api_keys_cherry_picking_new.c */